Advanced LIGO Two-Stage Twelve-Axis Vibration Isolation and Positioning\n Platform. Part 2: Experimental Investigation and Tests Results

This paper presents the results of the past seven years of experimental\ninvestigation and testing done on the two-stage twelve-axis vibration isolation\nplatform for Advanced LIGO gravity waves observatories. This five-ton\ntwo-and-half-meter wide system supports more than a 1000 kg of very sensitive\nequipment. It provides positioning capability and seismic isolation in all\ndirections of translation and rotation. To meet the very stringent requirements\nof Advanced LIGO, the system must provide more than three orders of magnitude\nof isolation over a very large bandwidth. It must bring the motion below\n10^(-11) m/(Hz)^0.5 at 1 Hz and 10^(-12) m/(Hz)^0.5 at 10 Hz. A prototype of\nthis system has been built in 2006. It has been extensively tested and analyzed\nduring the following two years. This paper shows how the experimental results\nobtained with the prototype were used to engineer the final design. It\nhighlights how the engineering solutions implemented not only improved the\nisolation performance but also greatly simplified the assembly, testing, and\ncommissioning process. During the past two years, five units have been\nconstructed, tested, installed and commissioned at each of the two LIGO\nobservatories. Five other units are being built for an upcoming third\nobservatory. The test results presented show that the system meets the motion\nrequirements, and reach the sensor noise in the control bandwidth.\n